1. Field of the Invention
The present invention relates to a multifunctional scalpel usable as a traditional cutting scalpel and usable for dermatotomy or “skin nick” in percutaneous procedures. In particular, the multifunctional scalpel includes elements for engagement to a guide wire, a scalpel blade for safety, positioning the scalpel blade for piercing, and positioning the scalpel blade for conventional cutting.
2. Description of the Related Art
Percutaneous medical procedures use a needle-puncture of the skin to gain access to an internal location such as a blood vessel, hollow internal cavity, internal organ or other internal location. In many applications, percutaneous medical procedures are preferred over “open” surgery which has more complications. Most percutaneous medical procedures are a variation of the Seldinger technique which involves inserting a hollow needle or trocar into a desired internal location and passing a round-tipped guide wire through the hollow needle until a leading end of the guide wire exits the trocar at the desired internal location. The trocar is then removed by advancing it along the guide wire to its trailing end. While the trocar punctures the skin and installs the guide wire into a blood vessel or other internal cavity, the initial puncture surrounding the guide wire usually needs to be enlarged using a scalpel or other cutting or piercing instrument. After the initial puncture surrounding the guide wire is enlarged, a hollow “sheath” or blunt cannula is passed along the guide wire and inserted through the enlarged puncture wound. The hollow sheath has a larger lumen passing along its axial length and is guided to the desired internal location by the guide wire. Once the sheath is in place, the guide wire is removed and various surgical tools can be installed through the sheath lumen to the desired location.
The procedure for enlarging the initial needle puncture surrounding the guide wire is referred to as a dermatotomy or “skin nick”. Ideally, the dermatotomy is substantially coincident with or immediately adjacent to the guide wire entry point. In addition, the depth and size of the dermatotomy may vary for different surgical procedures, different instrument sheath sizes and different body locations. Heretofore the dermatotomy was performed by a surgeon using a conventional scalpel having its cutting blade fully extended and locked in place while held in a free hand and using only visual guidance to position dermatotomy coincident with or immediately adjacent to the guide wire entry point and to make the dermatotomy with a cut depth and length that is suitable for the situation. Even under ideal circumstances, such as with good lighting and a well positioned patient, a dermatotomy performed with a conventional scalpel may not be optimal when it is performed free hand. Moreover, a dermatotomy may need to be performed under non-ideal circumstances, e.g. when performed quickly in an emergency, when preformed in a low light level or when performed with the patient poorly positioned and such procedures are even more difficult to perform optically with a free hand held conventional scalpel.
More recently tools have been developed for guided dermatotomy procedures. In particular, US 2004/0181246 by Heppler, discloses a scalpel configured with a pair of wire guides attached to the scalpel and configured to be guided along the guide wire so that the scalpel blade is guided to the location where the dermatotomy needs to be placed, e.g. coincident with or immediately adjacent to the guide wire entry point. As further disclosed in Heppler, the wire guides can be attached to the scalpel handle, to the scalpel blade, to a plate sandwiched between the scalpel handle and the scalpel blade or to a movable safety sheath that fits over the scalpel blade and partially over the scalpel handle. While the improved scalpel taught by Heppler is usable for both freehand cutting and guided dermatotomy procedures, the movable safety sheath disclosed by Heppler appears difficult to use. Moreover, it is unclear from the disclosure how the safety shield is attached to the scalpel or moved from multiple operating positions including a depth stop position. Accordingly there is a need for an improved scalpel usable for guided dermatotomy procedures as well as for free hand cutting that provides a more reliable blade retracting mechanism and blade locking mechanism for locking the blade in a plurality of different positions and a more robust mechanism for setting a blade depth stop position for desired cut depths, such as for consistently performing a dermatotomy with a desired length and cut depth.